Ultrasone seems to be a brand that has very, VERY, mixed views and many different interpretations of how each model sounds. I'd try and audition them before you buy if possible.
I own the 780's and they have pretty forward mids. They are marketed as a "movie watching" headphones so it makes sense that they have forward mids for voices and such. (I'm not drawing a conclusion there where just because it "makes sense" that it is the way it is. They sound to me that...

Well you're gonna have to live with the looks so what ever looks best to you
Personally I think the colors in the pictures above go together well. My speakers are all black but have a gray/silver driver and edging and I think it looks pretty sweet.

I don't see the need to spend $800 on speakers. It just won't be worth it in my eyes. What ever you decide to do with the money you've saved is up to you. The sound quality is just fine using the HDMI out on my laptop. The receiver is the DAC when you do this, so no need to buy a separate DAC if you hook up via HDMI. Make sure though that your laptop outputs audio through the HDMI port and not just video.